The present invention relates to a method of regulating and controlling an internal combustion engine forming part of a hybrid power unit of a self-propelled vehicle.
Known methods of controlling an internal combustion engine, in particular a diesel engine, are based on thousands of work points obtained from engine work graphs showing, for example, power and torque as a function of the rotation speed of the drive shaft. Since little ready-made data is normally available, constructing reliable maps for a given engine is an enormous job in terms of data acquisition and, obviously, in terms of time and work, and seriously complicates the electronic central control unit regulating the actuator governing the diesel engine injection pump.
It is an object of the present invention to provide a feasible, approximate solution to the problem of regulating the injection of a diesel engine to ensure low consumption, low emission of harmful gases, a low noise level, and a long working life of the engine.
The method according to the present invention can only be applied to a hybrid power unit, which, as will be seen, provides for separating control of optimum engine conditions from the actual traction power required.
Since the engine-wheel gear ratio is variable continuously, vehicle speed may vary independently of engine speed, which may therefore be selected to suit a given vehicle speed, which at best should provide for reducing specific fuel consumption (SFC), pollutant emissions, noise level, and engine wear, while at the same time preserving the elasticity and control response of the engine.
For a given traction power, current regulating methods fail to provide for transmitting the power of the engine under maximum-torque conditions. Since specific fuel consumption of an engine is minimum under maximum torque conditions, and since the noise level also increases alongside engine speed, the engine, for a given traction power, should be operated at minimum speed while at the same time providing the mean traction power required by the terrain. For this to be done, the operating point of the engine must be located on the maximum-torque curve, which means determining the injection pump setting enabling the engine to supply the necessary instantaneous power in the best conditions referred to above.
According to the present invention, there is therefore provided a method of regulating and controlling an internal combustion engine connected to a hybrid power unit of a self-propelled vehicle, the method employing a first graph showing the power transmitted by the engine as a function of the rotation speed of a drive shaft, and for different injector openings of a power-regulating injection device; and a second graph showing the torque transmitted by the drive shaft as a function of the rotation speed of the drive shaft, and for different injector openings of the power-regulating injection device.
It is another object of this invention to provide a method of regulating and controlling an internal combustion engine by dividing the y-axis of a first graph arbitrarily into a number of ranges advantageously, though not necessarily, of the same size; inserting on the y-axis of the first graph the power value required to operate the self-propelled vehicle, so as to single out one of the ranges; locating on the first graph the maximum power value in the range singled out; determining on the first graph the drive shaft rotation speed corresponding to the maximum power value located; transferring the rotation speed determined to said second graph to locate the corresponding torque value; locating on said second graph, at the point of intersection between the maximum-torque curve and the vertical line through the drive shaft rotation speed determined, the partial-torque and relative injector opening curve through the point; tracing the partial-torque curve on said second graph up to the intersection with the x-axis to determine the idling speed of the engine at the given injector opening; and determining the position of the injection pump regulating member so as to inject fuel into the engine according to the injector opening determined.
These and other objects, features and advantages are accomplished according to the instant invention by providing a method of regulating and controlling an internal combustion engine forming part of a hybrid power unit of a self-propelled vehicle, the method employing a first graph showing the power transmitted by the engine as a function of the rotation speed of a drive shaft, and for different injector openings of a power-regulating injection device; and a second graph showing the torque transmitted by the drive shaft as a function of the rotation speed of the drive shaft, and for different injector openings of the power-regulating injection device; the second graph also showing the injector opening of the power-regulating injection device.